Automatic telephone system.



E. H. CLARK.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION HLED SEPT- 30. 1915..

1,245,436. I Patented Nov, 63,1917.

2 SHEETS-SHEET I.

Selector Line-finder /nven/ar:

Q1 rvvesf 's F w Edgar hf C/ak/r E. H. CLARK.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT. so. 1915.

1 5245, 136. P atenwd Nov. 6, 1917. I

2 SHEETS-SHEET 2.

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9.. Edqa/ H. (Ya /r UNTTED STATES PATENT @FFTfiE.

EDGAR HARRISON CLARK, OF NEW YORK, N. Y., ESSIGNOR, BY It IESNE ASSIGNMENTS, TO XVE$TERN ELECTRIC COMPANY, INCORPORATED, A CGBPOBATION OF NEVI YORK.

AUTOMATIC TELEPHONE SYSTEM.

Application filed September 30, 1915.

To all whom it may concern:

Be it known that I, EDGAR HARRISON CLARK, citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the I following is a full, clear, concise, and exact description.

This invention relates to automatic telephone systems of the two-wire multiple type, that is, automatic systems in which but two wires (the talking conductors) are multiplied through the various switches used in establishing a talking connection. A system of this general character is shown in an application of Charles L. Goodrum, Serial No. 35,326, filed June 21, 1915.

One of the objects of the present inven tion is the provision of a test circuit for the line finder switch wherein a test relay is provided for each line finder.

Another feature of the invention resides in the provision of a control relay at the selector switches which is maintained energized in parallel to a portion of the talking circuit in order to control the release of the select-or switches.

Another feature of the invention resides in circuits at the connector switch wherein the operation and the release of the connector switch is controlled over one of the talking conductors while the test takes place over the other talking conductor.

A further object of the invention resides in novel ringing control circuits wherein the ringing is controlled directly by an armature and contact of the escape or side switch magnet.

Figures 1 and 2, with Fig. 1 at the left, show the circuits of the invention and diagrammatically indicate the apparatus employed therein. Fig. 3 illustrates the manner in which the windings of the line relay of the succeeding selector switch are connected. Any step-by-step two-movement switch may be employed with the circuits shown. A switch of this general character is shown in patent to Keith and Erickson No. 815,17 5, although a switch such as disclosedin an application of Oscar F. Forsberg, Serial No. 6302, filed February 5, 1915, will preferably be employed. It is to be understood Specification of Letters Patent.

Patented Nov. 6, 1917.

Serial No. 53,440.

that in practising this invention only two brushes will be employed on each switch, and each set of stationary contacts will consist of but two contacts. I

lVith each switch a circuit-changing device for controlling certain operating circuits at its respective switch is employed. These devices may be of the general character of the switch shown in the above mentioned patent and referred to therein as a side switch. But a circuit-controlling device, such as shown in the above mentioned Forsberg application, will preferably be employed. Such a circuit-controlling device may be caused to effect circuit changes either upon the energization or upon the deenergization of its operating or escape magnet, as described in said application.

Although the invention is described in a system using step-by-step switches some of the features disclosed are applicable to systems employing other types, as power driven switches.

lVit-h each line is associated a line relay 1 and a cut-0E relay 2 individual thereto. The lines are arranged in groups of ten each, and for each group of ten lines a pair of control relays 3 and 4, shown within the dotted rectangle at the lower left corner of Fig. 1, are employed. The apparatus within this dotted rectangle is common to all'the ten lines of a group. The switches employed in the present embodiment of this invention are hundred-point switches, the contacts being arranged in ten groups'of ten contacts in a group.

As the circuits employed in this system are of a very simple character, it is believed that the invention will be readily under- I stood from the following description in which the establishment of a successful and an unsuccessful. connection is described, and also the manner of releasing the switches in either instance.

Ve will assume that the subscriber at the the calling subscriber removing his receiver from its hook, a circuit is established from battery, through the left winding of line relay 1, back contact and left armature of cut-off relay 2, over the left side of the line,

through the substation apparatus of the calling subscriber, back over the right side of the line, the right armature and contact of relay 2 and the right winding of relay 1, back to battery. Relay 1 is energized and completes a circuit from battery, through relay 3, left armature and contact of relay at to ground, through the right armature of relay 1. Relay 3 pulls up and looks through its left armature and contact. When relay 3 pulls up, it interrupts the circuit of the starter wire 5 at its right armature and back contact, and at its front contact it completes a circuit from battery, through rotary magnet 6, its individual interrupter 7, side switch wiper 8, back contact and armature of test relay 9, normally closed contact 10, contact and armature of release magnet 11, and relay to ground through the armature of relay 3. Relay 4 pulls up andinterrupts the circuit extending from the line relay at any other line in the group of the calling subscriber, and also opens the circuit for the release magnet 11. The circuit through the rotary magnet 6 causes the switch to be rotated step by step from group to group of the lines until the group-selecting brush 12 of the switch engages the contact individual to the group of the calling line, which will be connected to ground through the right armature of the line relay 1 of the calling line.

7 armature of relay 1,

left armature of relay 1.

magnet 11 to ground, through the right armature of relay 3. The vertical magnet is then operated, and under the control of its individual interrupter the switch brushes 1T,

18 are moved from line to line of the group of the calling subscriben When the switch brushes engage the terminals of the calling line, a circuit is established from battery, through the right winding of cut-off relay 2, left armature and contact of relay 1, brush 17, side switch wiper 19, and the two windings of test relay 9 in series to ground. Relay 9 is so adjusted that it will not pull up through the two windings of relay 2 in series, but will pull up when the left winding is shunted by the Relay 9 is energized by the above described circuit, and

in pulling up, completes a circuit from battery through magnets 6 and 13 in series,

lower inner contact and armature of relay 9, ofi-normal contact 10, back contact and armature of relay 11 to ground, through the right armature and contact of relay 3. The escape magnet 13 will be energized by this circuit, but magnet (3 will not. This moves the side switch to position 3.

In position 3 a circuit is established from battery, through the right winding of relay 2, left armature and contact relay 1, brush 17 and side switch wiper 19 to ground. Relay 2 attracts its armatures and interrupts the circuit for relay 1, which, in falling off, deenergizes relay 3. Relay 3, in retracting its armature, interrupts the circuit for relay at and ret-stablishes the starter circuit from wire 5. lVhen the side switchmoves to position 3, the circuit for the test relay 9 is interrupted and this relay falls off. A circuit is now established from battery, through magnets 6 and 13, side switch wiper 14, and the back contact and armature of escape magnet 13 to ground. Escape magnet 13 is energized but is immediately deenergized by the attraction of its armature, thus causing the side switch to move to position 1. now extends from battery through both windings of said relay in series, brush 17, wiper 19, wiper 25 and contact and armature of magnet 26.

In position a the side switch wiper 8 extends the starter circuit on to the next succeeding switch This starter circuit may now be traced from the preceding switch through wire 5, back contact and right armature of relay 3, relay 1, contact and armature of release magnet 1l,'contact 10, armature and back contact of relay 9, and wiper 8 to the starter wire 5 extending to the next succeeding switch.

Had the subscriber replaced his receiver upon the hook during 'the orief interval in which selection was taking place, the line relay 1 would have been de'elnergized, thus causing the de'e'nergization of relay 4. This would complete a circuit from battery, through release magnet 11, rotary off-normal contact 20, right armature and contact of relay 1, back contact and armature of escape magnet 21 at the first selector switch, and back contact and armature of line relay 22 at said selector switch to ground, thus causing the release of the line finder switch period.

If, for any reason, the escape magnet 13 is not operated when the brush 12 passes over the group contact of the calling line,

A holding circuit for relay 2 found in this group, the brushes will move to the end of the series of contacts. Upon the tenth step, ofi-normal contact 10 will open the circuit for relay 4, which, in retracting its armature, will complete a circuit from battery, through release magnet 11, contact 20, right armature and contact of relay 4, back contact and armature of magnet 21, and back contact and armature of relay 22. This will cause the return of the line switch to normal, when it will again start hunting for the calling line group.

The subscriber now operates his dial to cause group selection at the first selector switch shown at the right of the dotted line in Fig. 1.

Then the line finder side switch moved to position 4, a circuit was completed from battery, through the right winding of line relay 22, wiper 23, wiper 24, brush 18, over the subscribers line, back through the left armature and front contact of cut-off relay 2, brush 17, wiper 19, and wiper 25 to ground, through the contact and armature of release magnet 26. Relay 22 attracts its armature and completesa circuit from battery, through escape magnet 21, vertical olfnormal contact 27 and rotary off-normal contact 28 to ground. Magnet 21 is energized but does not move the side switch. WVith each interruption of the subscribers line by the sending device, relay 22 will retract its armature and complete a circuit from battery, through rotary or group selecting magnet 29, front contact and armature of magnet 21 to ground, through the back contact and armature of relay 22. Thus, the brushes 30 and 31 will be stepped from group to group until the termination of the series of impulses. With the first rotary step, spring 28 leaves its lower con tact and engages its upper contact, and magnet 21 being slow to release, is maintained energized during the rest of the series at the back contact of relay 22. At the termination of the series, however, relay 22 remains energized and escape magnet 21 falls off, moving the side switch wipers to position 2.

In position 2 a hunting circuit is established from battery through the vertical or hunting magnet 32, its individual interrupter 33, and side switch wiper 34 to ground, through the armature of test relay 35. Then the switch brushes 30 and 31 engage the contacts of an idle trunk, the lower conductor of said trunk will be connected directly to ground through the back contact of relay 36 and the back contact of release magnet 37, and an energizing circuit will be established from battery through the test relay, side switch wiper 3S, brush 30 to ground at the next switch. The test relay 35 is so adjusted that it will not be energized if the resistance 39 is included in its circuit.

The energization of the test relay 35 over the circuit hereinbefore traced completes a circuit for the escape magnet 21, which, upon energization, moves the side switch wipers to position 3. In position 3 the circuit through the right winding of relay 22 is interrupted, but the left winding of said relay is included in a circuit in parallel with the resistance 40 in the lower talking conductor. 7 Thus, relays 2 and 22 will be main tained energized in series by a circuit extending from battery, through both windings of relay 2, left winding of relay 22 to ground at the back contact and armature of release magnet 37. This circuit will first extend through the back contact and armature of relay 36, but the subsequent inclusion of the resistance 39 in the circuit would not cause the retraction of the armatures of relays 2 and 22.

While only one selector switch is shown in the present system, it is to be understood that other selector switches may be inserted between the first selector switch in Fig. 1 and the connector switch shown in Fig. 2. The circuits of these succeeding selector switches might be substantially identical with that shown in Fig. 1. It would be preferable, however, to include the left winding of the control or line relay of one or more of the succeeding selector switches in shunt circuits from the other talking conductor, in order that a balanced condition of the line may be more readily maintained. This is shown in Fig. 3 in which the manner of connecting the windings of the line relay 22 of the succeeding selector switch is represented. I

The subscriber now operates his dial to send the tens or group selecting series of impulses to the connector switch shown on Fig. 2. When the selector side switch wentto position 3, a circuit was closed from battery, through stepping relay 41, over the upper side of the line, over the subscribers line, back through the left armature and front contact of. cut-off relay 2 to ground, through the left armature and back contact of magnets 36 and 37 Relay 41 was energized and completed an energizing circuit for relay 36. The retraction of the left armature of relay 36 removed the shortcircuit from around resistance 39, thus caus ing the trunk leading to this final connector switch to test busy. Each interrup tion of the circuit by the substation sending device will cause the retraction of armature of relay 41, which will complete a circuit from battery, through the rotary magnet 42, side switch wiper 43, front contact and right armature of relay 36 to ground, through the back contact and armature of relay 41. Each deenergization of relay 41 will also complete a circuit through relay 44. This relay being slow to release,

will remain energized during the series of impulses. Upon the repeated energization of stepping magnet 42, the brushes 45 and 46 of the connector switch move from group "cup of the contacts of the subscribers terminating therein. Upon the termination of the series of impulses, relay 41 will remain energized, thus holding open the circuit for relay 44, which, inretracting its arn'iature, completes a circuit from battery, through escape magnet 47, side switch wiper 48, rotary ofienormal contact 49, and back contact and armature of relay 44 to ground. The escape magnet is energized and moves the side switch to position 2.

The subscriber now sends the units series of impulses. Each deenergization of relay 41 completes a circuit from battery, through the vertical stepping magnet 50, wiper 43, front contact and armature of relay 36, back contact and armature of relay 41 to ground.

Relay 44 is energized by the first impulse and remains up throughout the series, as be fore. lVhen relay 44 attracts its armatures, it interrupts the circuit for the escape magnet, which retracts its armatures, but this operation does not cause the side switch wipers to move. It is necessary that the escape magnet be deenergized during the units selection, as otherwise ringing current would be connected to connector switch brush Upon the termination of the units series of impulses, relay 44 retracts its armature completing a circuit from battery, through the escape magnet 47, contact and armature of ringing trip relay 61, side switch wiper 48, vertical off-normal contact 52 to ground, through back contact and armature of relay 44. This moves the side switch to position 3, when the test of the wanted line takes place. If the wanted line is idle, the full potential of the battery will be applied to the lower or test contact of the line through the windings of the cut-off relay 2. If, however, the line is busy as a calling line, this potential will be lowered by means of the circuit extending to ground through the resistance 39 at the connector switch, and if busy as a called line, the potential on the test contacts will be decreased by the circuit to ground through the right winding of the battery supply resistance coil 53. Therefore, if the line is idle, the current flowing over the circuit from the test contact to brush 46, side switch wiper 54, right armature and back cont-act of relay 44, and the two windings of the test relay 55 in series, will energize the test relay, which will complete a circuit from battery, through escape magnet 47, contact and armature of relay 51, wiper 48, front contact and armature of test relay 55 to ground. The escape magnet will be energized but will not cause the side switch wipers to move. Ringing current will now be supplied to the called subscribers line from generator 56, through ringing trip magnet 51, right armature and front contact of the escape magnet 47, over the upper side of the subscribers line to ground, through the called subscribers bell.

Upon the response of the called subscriber, the increased flow of current through relay 51 will cause it to attract its armature, thus interrupting the circuit of the escape magnet 47, which, in deenergizing, moves the side switch wipers into position 4, thus completing the talking circuit between the calling and called subscribers. If the wanted subscribers line is busy, test relay 55 will not attract its armature, and therefore the ape magnet will remain deenergized. The side switch being in position 3, the busy tone will be transmitted through the left armature and back contact of the escape magnet to the upper talking conductor, and thence to the calling subscriber, notifying him that the wanted subscriber is not available. As the right armature of the escape magnet will be retracted at this time, no ringing current would be applied to the wanted subscribers line.

The release of the several switches is controlled by the calling subscriber and takes place in the same manner whether or not the call is successful.

Upon the calling subscriber replacing his receiver upon the hook, the stepping relay 41 at the connector switch will be deenergized. The deenergization of relay 41 interrupts the circuit for relay 36, which, in retracting its armature, completes a circuit from battery, through release magnet 37, rotary off-normal contact 59, back contact and right armature of relay 36 to ground, through the back contact and armature of relay 41, thus causing the return to normal of the connector switch. The operation of release magnet 37 opens the circuit of relay 22 at the selector, which in retracting its armature will complete circuits for the release magnet 11 of the finder switch and for the release magnet 26 of the first selector switch as follows: from battery, through release magnet 11, rotary off-normal contact 20, armature and back contact of relay 4 to the back contact of escape magnet 21. A parallel circuit will be completed from battery, through release magnet 26 and the vertical off-normal contact 58 to the same back contact of magnet 21, and thence to ground through the armature of magnet 21 and the back contact and armature of relay thus causing the finder switch and the first selector switch to return to normal.

If the calling subscriber replaces his re ceiver on the hook at any time during the establishment of the connection to a selector switch or the connector switch, the return of the switches, which have been moved from normal, will be accomplished by means of circuits identical with the release circuits just traced.

IVhat is claimed is:

1. In a telephone system, a switch, incoming lines terminating in contacts at said switch, an outgoing line, means operated upon the initiation of a call on any of said incoming lines for moving said switch over the contacts of said incoming lines, a test relay at said switch for stopping the operation thereof, a line relay for each incoming line, and a circuit for said test relay completed when said switch engages the contacts of the incoming line upon which the call is initiated, said circuit ext-ending over a talking contact of said switch and a contact of the line relay of said incoming line.

In a telephone system, a subscribers line, a trunk line, an automatic finder switch, means for causing said switch to connect said trunk line to said subscribers line upon the initiation of a call thereon, a test relay for said switch, a cut-oil. relay for said sub scribers line, and an operative circuit for said relay extending through talking contacts of said switch and the cut-off relay of said line.

3. In a telephone system, a subscribers line, a trunk line, an automatic finder switch, means for causing said switch to connect said subscribers line to said trunk line upon the initiation of a call on said line, a test relay for said switch, a line relay and a cutoff relay for said line, a pair of windings on said cut-off relay, means controlled by said line relay for short-circuiting one of said windings, and an operating circuit for said test relay extending through a talking contact of said switch and one of the windings of said cut-off relay.

4. In a telephone system, a selector switch, a pair of talking conductors extending to said switch, a relay winding for controlling the operation of said switch included in series with one of said conductors, a second relay winding included in parallel with a portion of the other said conductor, a release circuit for said switch including a normally closed contact, said second winding being energized during conversation to hold open said normally closed contact.

5. In a telephone system, a selector switch, a pair of talking conductors extending to said. switch, a relay for controlling the operation and the release of said switch, and a pair of windings on said relay, one of said windings being included in series with one of said conductors and the other winding being included in parallel with a portion of the other said conductor.

6. In a telephone system, a selector switch, a pair of talking conductors extending to said switch, a relay, and a pair of windings on said relay, one of said windings being included in series with one of said conductors to control the operation of said switch, and the other winding being included in parallel with a portion of the other said conductor to control the release of said switch.

7. In a telephone system, a source of ringing current, a side switch magnet, a circuit including a contact and armature of said magnet for joining said source of current to a wanted subscribers line, a ringing trip relay in said circuit, and a circuit for said side switch magnet extending through a contact of said trip relay,

8. In a telephone system, a source of ringing current, a side switch magnet, a circuit including a front contact and armature of said magnet for joining said source of current to a wanted subscribers line, a ringing trip relay in said circuit, and a circuit for said side switch magnet extending through a back contact and armature of said trip relay.

In witness whereof, I hereunto subscribe my name this 29th day of September, A. D., 1915.

EDGAR HARRISON CLARK.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

